Phylogenetic analyses of various euglenoid taxa (Euglenozoa) based on 18S rDNA sequence data

18S rRNA genes (SSU rDNA) of five newly sequenced species were used as mole cular markers to infer phylogenetic relationships within the euglenoids. Tw o members of the order Euglenales (Lepocinclis ovata Playfair, Phacus simil is Christen), two of the order Eutreptiales (Distigma proteus Ehrenberg, D, curvata Pringsheim) and Gyropaigne lefevrei Bourelly et Georges of the ord er Rhabdomonadales were used in parsimony, maximum Likelihood, and distance analyses. All trees derived from SSU rRNA data strongly supported the mono phyletic origin of the Euglenozoa, with kinetoplastids as sister clade to t he euglenoids and Petalomonas cantuscygni Cann et Pennick diverging at the base of the monophyletic euglenoid lineage. The data also supported the the ory that phagotrophic euglenoids arose prior to osmotrophs and phototrophs. A lineage of Peranema trichophorum Ehrenberg and all sequenced Euglenales formed a sister clade to the osmotrophs, This suggests that the evolution o f phototrophy within the euglenoids radiated from a single event.